Objective: Here we propose a retrospective study on 319 subjects already investigated for a correlation between polymorphisms and intoxication by heavy metals, which, in some cases, lead to possible ...cancer alterations, in order to identify, through mathematical model, the analogies between heavy metals-induced epigenetic alterations and those caused by COVID-19. Patients and Methods: A total of 319 patients, 182 males and 137 females with a median age of 44 for the former and 31 for the latter, have been studied between 2016 and 2019 by performing a hair mineralometry, analyzed with inductively coupled plasma mass spectrometry, and buccal swab followed by DNA extraction. Different polymorphisms have been investigated to find any correlations with heavy metals intoxication. Results: We found a correlation between some of the genotyped polymorphisms and altered levels of heavy metals in 86% of exanimated cases. According to estimates of our mathematical models, the described genetic susceptibilities could raise up the risk of contagion for COVID-19. Conclusions: The carriers of the above polymorphisms are probably more at risk of accumulating toxic metals, thereby, contracting severe oxidative damage. The mathematical model herein applied suggested us COVID-19 could use the same mechanism described for toxic metals. If these preliminary data will be confirmed, we suggest genetic screening as optimum solution to identify both cancer risk subjects and those highly exposed to virus contagion.
Purpose: To determine the accuracy of VMAT treatment planning and delivery for patients undergoing radiotherapy in the head and neck. Method and Materials: A dosimetric study of a typical head and ...neck treatment plan has been carried out using Chamber, film and TLD's placed inside an anthropomorphic phantom. Lateral and AP port films were taken to verify the isocenter prior to treatment. Multiple treatments were performed to assess the reproducibility and uncertainty in the TLD measurements. Gafchromatic film was used between the phantom slices and then analyzed as an independent check on the TLD results. The two data sets, from TLDs and films, were then compared with the treatment planning system dose calculations. Results: The measured dose to the primary planning tumor volume agrees with the planning system within 2%. The comparison of the measured dose to the secondary tumor volume ranges from 3–6% and the spinal cord comparison ranges from 3–10%. Conclusion: This new Smart Arc treatment, VMAT, has great benefits to the patient in that patient motion and internal motion of the tumor is dramatically reduced. Challenges arise in predicting the dose near heterogeneities between the treatment planning system and actual measurement.
The Majorana Collaboration has assembled an array of high purity Ge detectors to search for neutrinoless double-beta decay in 76Ge with the goal of establishing the required background and ...scalability of a Ge-based next-generation ton-scale experiment. The Majorana Demonstrator consists of 44 kg of high-purity Ge (HPGe) detectors (30 kg enriched in 76Ge) with a low-noise p-type point contact (PPC) geometry. The detectors are split between two modules which are contained in a single lead and high-purity copper shield at the Sanford Underground Research Facility in Lead, South Dakota. Following a commissioning run that started in June 2015, the full detector array has been acquiring data since August 2016. We will discuss the status of the Majorana Demonstrator and initial results from the first physics run; including current background estimates, exotic low-energy physics searches, projections on the physics reach of the Demonstrator, and implications for a ton-scale Ge-based neutrinoless double-beta decay search.
Purpose: To calculate the percentage depth dose of any irregular shape electron block using the lateral build‐up‐ratio method.Methods: Percentage depth dose (PDD) curves were measured using 6, 9, 12, ...and 15 MeV electron beam energies for applicator cone sizes of 6×6, 10×10, 14×14, and 20×20 cm2. Circular cutouts for each cone were prepared from 2.0 cm diameter to the maximum possible size for each cone. In addition, three irregular cutouts were prepared. The scanning was done using a water tank and two diodes ‐ one for the signal and the other a stationary reference outside the tank. The water surface was determined by scanning the signal diode slowly from water to air and by noting the sharp change of the percentage depth dose curve at the water/air interface.Results: The lateral build‐up‐ratio (LBR) for each circular cutout was calculated from the measured PDD curve using the open field of the 14×14 cm2 cone as the reference field. Using the LBR values and the radius of the circular cutouts, the corresponding lateral spread parameter (sigma) of the electron shower was calculated. The PDD curves of the irregular cutout sizes were calculated using the sigma values of the 2 cm and the 3 cm diameter cutout sizes. Finally, the calculated PDD curves were compared with measurements of the irregular cutouts Conclusions: The PDD curves for the irregular cutout calculated using the sigma value of the 2.0 cm diameter cutout agreed with the measured PDD curves within 2% for 6MeV and 4% for 12 MeV. On the other hand, using the average sigma values of the 2 and 3 cm diameter cutouts reduced the difference by a factor of two. The result of the calculated sigma value showed that at a given depth and energy, the sigma value increases with cutout size.
Purpose: The efficiency of a treatment plan is extremely important to reduce a patient's time on the table. Decreasing the amount of monitor units to achieve a prescribed dose will directly decrease ...this time. In this regard, two techniques of IMRT treatment delivery were tested and compared. Methods and Materials: The variable technique, which is the standard method of IMRT for Elekta, allows the secondary collimator to vary for each segment minimizing the MLC leakage. In the static technique, the secondary collimator remains fixed at the largest MLC segment for that particular beam. An anthropomorphic phantom was treated for two types of cancer to analyze each technique. A typical head and neck PTV was placed on the phantom's CT as well as a typical cervical cancer. Each plan was optimized using static and variable techniques to either account for or minimize the MLC leakage. TLDs were placed throughout the treatment regions to confirm the treatment plans. Additionally, a study is presented for patients being treated for bilateral lungs in which static and variable plans were created and analyzed. Results: The static and variable techniques provide similar dose coverage for the regions of interest. The difference comes when the total monitor units are computed. For the cervical treatment the monitor units are decreased from 938 to 751. The head and neck case had a much more dramatic decrease from 1685 to 744. The bilateral lung cases will be presented to show when a static treatment cannot reproduce the DVH of a variable treatment. Conclusion: A method is presented here in which monitor units can be minimized while maintaining the integrity of the treatment. There are limitations to this technique and an example is shown to demonstrate the need to carefully analyze treatment planning for each patient. Research sponsored by Elekta corporation.
The goal of the Majorana Demonstrator project is to search for 0νββ decay in 76Ge. Of all candidate isotopes for 0νββ, 76Ge has some of the most favorable characteristics. Germanium detectors are a ...well established technology, and in searches for 0νββ, the high purity germanium crystal acts simultaneously as source and detector. Furthermore, p-type germanium detectors provide excellent energy resolution and a specially designed point contact geometry allows for sensitive pulse shape discrimination. This paper will summarize the experiences the MAJORANA collaboration made with enriched germanium detectors manufactured by ORTEC®®. The process from production, to characterization and integration in MAJORANA mounting structure will be described. A summary of the performance of all enriched germanium detectors will be given.
The Majorana Demonstrator is a planned 40 kg array of Germanium detectors intended to demonstrate the feasibility of constructing a tonne-scale experiment that will seek neutrinoless double beta ...decay (0νββ) in 76Ge. Such an experiment would require backgrounds of less than 1 count tonne-year in the 4 keV region of interest around the 2039 keV Q-value of the ββ decay. Designing low-noise electronics, which must be placed in close proximity to the detectors, presents a challenge to reaching this background target. This paper will discuss the Majorana collaboration's solutions to some of these challenges.
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